This invention relates to an identification tag for fitting on to an electrical cable to provide enhanced safety at a connection between the cable and another component and also cable identification. The invention further relates to a method of providing electrical shielding and identification for a cable at a connection between the cable and an electrical component.
This invention may be used in many electrical wiring situations, though it is primarily concerned with the safety and identification of electrical cables connected to single phase and three phase electricity meters. As such, the invention will be described hereinafter solely in relation to this situation though it is to be understood that the invention is not limited to this.
In many electrical wiring installations, it is essential that adequate safety be assigned to a connection between an electrical cable and a component to which the cable is connected. Further, it may be advantageous, or sometimes a requirement of the wiring regulations, to provide an identification of a cable carrying mains electricity, including easily visible and clear markings. A particular case in point is with supply cables connecting an incoming electrical supply to an electricity meter and feed cables connecting the electricity meter to an isolator switch, a consumer unit for distribution around a building or other electrical component.
The supply and feed cables to an electricity meter are usually referred to as “tails” and, for the domestic environment, normally have conductors of 25 mm2 cross-section or 16 mm2 cross-section. The electrical cables typically have a layer of insulation around the conductors and an outer sheath surrounding the insulation. Often, the insulation and sheath (if provided) are of a uniform grey colour and so do not serve to identify the whether the cable is a “live” or “neutral” cable. In some cases, however, one or both of the sheath and inner insulation may be coloured to denote the polarity of the electrical cable.
When a cable is to be connected to an electricity meter, the insulation and, if provided, the outer sheath must be cut away to expose the conductors which are then fitted into a connector within the meter and are clamped in place by means of screws provided as a part of the connector. It is important that there is no access to the conductors of the cable or the connector of the meter in the region of the connection. This is important for safety purposes, and also in order to prevent fraudulent tapping of electricity from the supply cables to the meter before the electricity has been metered.
In order to enhance the safety of the connections at an electricity meter and also to restrict access to the conductors of the cable or the connectors of the meter, it is known to provide the connectors within a meter housing at the inner end of a recess in the housing. Such a recess may be of uniform circular cross-section or may be generally conical. Further, it is known to provide an upstanding external rim on the housing around the recess leading to the connectors. With this arrangement the object is to ensure that the conductors of the cable cannot be accessed once fitted to the connector within the meter housing.
Following the preparation of an end portion of the cable by stripping away the insulation and the outer sheath to expose a pre-set length of the cable conductors, it is also known to fit a flanged collar to the cable. The flanged collar effectively enlarges the diameter of the cable at cut end of the insulation and aims to provide enhanced safety by reducing access to the conductors and the connectors within the meter. Most of the known collars have a protrusion which projects into a recess in the meter housing leading to the meter connector to assist safety, for example in the event that the insulation creeps back from where it was cut or that too great a length of the conductors was exposed. The known collars also have a radial flange at or adjacent an end of the collar intended to lie adjacent the exposed conductors such that the flange will seat against an outer end of the recess in the meter housing or against a surrounding rim, if provided. However, rather than enhancing safety and security, it is found that flexing of a cable carrying such a collar causes the flange of the collar to lever against a part of the meter housing. By pulling the cable to one side that leverage makes it relatively easy to gain access to the conductors of the cable between the collar or flange and the meter housing.
There is, therefore, a need to provide an improved collar which addresses the issues of both electrical shielding and safety of the conductors of a cable at a connection to an electrical component such as an electricity meter.
Current wiring regulations also require the supply cables to an electricity meter and the feed cables from a meter to a consumer unit, isolator switch or other electrical component to be appropriately identified both by colour and with symbols typically in the form of letters and/or numerals.
The colour may be provided by the colour of the outer sheath of the cable itself, by the use of coloured insulation tape wound around the cable, or by a collar fitted around the cable. In the case of an incoming supply cable to a meter, the live cable should carry a symbol in the form of a single letter L and the neutral cable a single letter N. In the case of a feed cable from a meter, the live cable should carry two letters L and the neutral cable two letters N. Further, in the case of a cable to certain specified items of electrical equipment, the live cable may be required to carry three letters L.
Appropriately coloured self-adhesive tape may be wound around the cables adjacent the connection thereof to an electricity meter. Brown tape may be used for the live cable and blue tape for the neutral cable, in accordance with the European regulations for a single phase supply. Further, the supply cables from the electricity supply to the meter may each carry one band of tape, and the feed cables from the meter to the consumer unit, isolator switch or other electrical component may carry two adjacent, but spaced apart, bands.
Symbols may be provided on the coloured tape, for example the letters L or N. Another possibility is for the symbols to be provided on separate components which are fitted to the cable either before or after the cable is connected to the meter. For example, it is known to use coloured cable ties having the letters marked on the tail of the tie. Once fitted, the cable ties are typically trimmed by cutting away the unwanted part of the tail. Each cable tie or coloured tape will include a band or series of repeated symbols along its length. To mark a cable with a single symbol, such as a single letter L, a single cable tie or strip of tape is wrapped around the electrical cable. To mark a cable with two symbols, such as a double letter L, two cable ties or strips of tape are wrapped around the electrical cable. As such, a single coloured cable tie may be used on an incoming supply cable to a meter and two coloured cable ties on the feed cable from the meter. It will thus be appreciated that six cable ties are required to mark the two incoming and two outgoing cables to an electricity meter, and in the case of a three phase meter twelve cable ties are required. The fitting of these is time-consuming and, of course, an electrician must carry a significant inventory of components in order to be able to adequately mark the cables associated with a meter.
The problem of adequate cable marking for an electricity meter is becoming more acute as there is a programme under way in the UK and elsewhere to replace all existing traditional electricity meters with smart meters. This requires a visit by an operative to each existing meter to check and identify the polarity and phase (in the case of a three-phase electricity supply) of the cables connected to the meter. Once identified, the cables are suitably marked before being disconnected from the meter. The existing meter is then removed and the replacement smart meter mounted in its place, whereafter the cables must be correctly connected to the smart meter. With a simple domestic supply there will be four cables connected to the traditional electricity meter, but with a three phase supply there will be eight such cables, and there may be further cables connected to the meter for example associated with other supply functionality such as a night time tariff. Depending upon when the original meter was installed those cables may carry no identification markings, or may be incompletely or inaccurately marked. As such, following disconnection of the cables from the existing meter, there could be a very high risk of confusion as to which cable is which when reconnecting the cables to the replacement meter unless steps are taken to identify the cables before disconnection from the existing meter and then marking the cables as appropriate.
In an attempt to ensure adequate cable identification for the future, current regulations specify that the cables connected to a new or replacement electricity meter must be appropriately identified, both by colour and symbols to show the function of the cable. These regulations must, therefore, be adhered to on replacing a meter, but the possible confusion of the cables connected to an existing meter must be addressed in order to ensure that, when an existing meter is replaced by a smart meter, the cables are appropriately identified before removal from the existing meter so that the cables are not confused when connected to the connectors of the replacement meter.
It is an aim of this invention to provide a device for attaching to an electrical cable that addresses one or more of the issues described above.